1. Field of the Invention
The present invention relates to a tape drive apparatus corresponding to a tape cassette that is used for data storage, for example.
2. Description of the Related Art
What is called the tape streamer drive is known as a drive apparatus capable of recording and reproducing digital data on and from a magnetic tape. This tape streamer drive can have an enormous recording capacity of about tens to hundreds of gigabytes, for example, though it depends on the tape length of a tape cassette as a medium. Therefore, this tape streamer drive is widely used for such purposes as backing up data that is recorded on a medium such as a hard disk of a computer main body. Further, this tape streamer drive is considered suitable for storage of, for example, image data having a large data size.
For example, a tape streamer drive of the above type is proposed which records and reproduces data by using an 8 mm VTR tape cassette as a recording medium and employing helical scanning by a rotary head.
For example, the above tape streamer drive using an 8 mm VTR tape cassette employs the SCSI (small computer system interface) as an input/output interface for recorded or reproduced data.
At the time of recording, data supplied from a host computer, for example, is input via a SCSI interface. Input data is transmitted in the form of data units each having a prescribed fixed length, and received data is compressed according to a prescribed scheme when necessary and temporarily stored in a buffer memory. The data stored in the buffer memory is supplied to a recording/reproduction system in a prescribed fixed-length unit called a group each time and recorded on the magnetic tape of a tape cassette by a rotary head.
At the time of reproduction, data on a magnetic tape is read out by the rotary head and temporarily stored in the buffer memory. The data that is output from the buffer memory is expanded if it was compressed at the time of recording, and then transmitted to the host computer via the SCSI interface.
The data recording area on a magnetic tape can be divided on a partition-by-partition basis. The tape streamer drive can perform data reproduction and writing on respective partitions independently of each other.
Incidentally, in a data storage system consisting of a tape streamer drive of the above type and a tape cassette, to properly perform a recording or reproducing operation on the magnetic tape of the tape cassette, various kinds of information relating to positions on the magnetic tape and information relating to a use history etc. of the magnetic tape are necessary as, for example, management information that is utilized by the tape streamer drive to manage recording and reproducing operations etc.
In view of the above, for example, it has been conceived to provide an area of such management information at the head of a magnetic tape and the head of each partition.
The tape streamer drive reads out necessary management information by accessing such management information areas before performing a data recording or reproducing operation on the magnetic tape, and performs various processing operations based on the management information so that the ensuing recording or reproducing operation will be performed properly.
When the data recording or reproducing operation is finished, to rewrite the contents of pieces of management information that need to be changed as a result of the recording or reproducing operation, management information areas are accessed again and their information contents are rewritten. A preparation for the next recording or reproducing operation is thus made. Then, the tape streamer drive performs, for example, unloading and ejection of the tape cassette.
However, when either a recording operation or a reproducing operation is performed based on management information in the above manner, at the start of the operation the tape streamer drive needs to access the management information area at the head of the magnetic tape or the head of a partition. Also at the end of the operation, the tape streamer drive needs to access such a management information area to write/read information to/from it. That is, loading or unloading cannot be performed in a state that data recording or reproduction has just been finished, that is, in a state that a halfway position of the magnetic tape is located at the head-acting position.
In the case of the tape streamer drive, since access requires physically feeding a magnetic tape, it takes a considerable time to access a management information area at the head of the magnetic tape or the head of a partition at the end of a recording or reproducing operation. In particular, in a case where data recording or reproduction has finished in a state that a point of the magnetic tape that is physically very distant from the management information area is located at the head-acting position, the necessary tape feed length is long accordingly and hence the feeding needs an extra time.
As described above, in the data storage system using a tape cassette as a medium, the time required until completion of one recording or reproducing operation, that is, the time taken by access operations that are performed between loading and final unloading of a magnetic tape, is relatively long. It is preferable that the time required for such a series of access operations be made as short as possible.
In view of the above, a technique has been developed that a nonvolatile memory, for example, is provided in a tape cassette and management information is stored in the nonvolatile memory.
In a tape streamer drive corresponding to such a tape cassette, an interface for writing and reading on the nonvolatile memory is provided and management information relating to data recording and writing on the magnetic tape is read from and written to the nonvolatile memory. Therefore, it is not necessary to rewind the magnetic tape so that the tape top, for example, is located at the head-acting position, at the time of loading or unloading; that is, loading or unloading can be performed even in a state that a halfway point of the magnetic tape is located at the head-acting position.
Further, this technique facilitates setting of more partitions on a tape and proper management of them.
For a tape cassette having a nonvolatile memory, the tape streamer drive is required to support use of the tape cassette in a mode in which a number of partitions can be set and used (for convenience of description, this mode is called xe2x80x9cmulti-partition modexe2x80x9d).
On the other hand, for a tape cassette not having a nonvolatile memory, only one or two partitions are supported conventionally. The tape streamer drive is also required not to cause any problem in using a tape cassette in such a mode (for convenience of description, this mode is called xe2x80x9cnormal modexe2x80x9d). Naturally, there is a request for enabling use of a tape cassette having a nonvolatile memory in the normal mode.
The present invention has been made in view of the above circumstances, and an object of the invention is therefore to provide a tape drive apparatus capable of supporting use of a tape cassette in both of a first mode (normal mode) and a second mode (multi-partition mode), as well as a tape drive apparatus capable of performing tape formatting including mode setting on a tape cassette.
To attain the above object, the invention provides a tape drive apparatus in which when a tape cassette is mounted, whether the tape cassette is of a first mode or a second mode is judged based on one or both of management information that is read out from the magnetic tape by tape driving means and management information that is read out from the memory by memory driving means, and operation setting is performed in accordance with the mode thus judged. That is, both modes can be supported by performing operation setting in accordance with the mode of a tape cassette.
According to a second aspect of the invention, there is provided a tape drive apparatus comprising storing means for storing mode information relating to a tape cassette; receiving means for receiving a command from a host apparatus; and control means for setting the tape cassette to a first mode or a second mode by causing one or both of tape driving means and memory driving means to write management information by using the mode information stored in the storing means when the receiving means receives a formatting command.
That is, according to the second aspect of the invention, the tape cassette itself is set to the first or second mode by tape formatting. The tape formatting including the mode setting is performed in accordance with a command that is supplied from the host apparatus.
When a tape cassette that has already been subjected to tape formatting is mounted, the operation of the tape drive apparatus is set in accordance with the mode of the tape cassette.